Biology subjects

Grob, P.

Publications and source records attributed to Grob, P..

3 recordsLinked to original sources

bioRxiv2025

Structural insights into transcriptional regulation by the helicase RECQL5

Transcription and its regulation pose a major challenge for genome stability. The helicase RECQL5 has been proposed as an important factor to help safeguard the genome, and is the only member of the human RecQ helicase family that directly binds to RNA Polymerase II (Pol II) and affects its progression. RECQL5 mitigates transcription stress and genome instability in cells, yet the molecular mechanism underlying this phenomenon is unclear. Here, we employ cryo-electron microscopy (cryo-EM) to determine the structures of stalled Pol II elongation complexes (ECs) bound to RECQL5. Our structures reveal the molecular interactions stabilizing RECQL5 binding to the Pol II EC and highlight its role as a transcriptional roadblock. Additionally, we find that RECQL5 can modulate the Pol II translocation state. In its nucleotide-free state, RECQL5 mechanically twists the downstream DNA in the EC, and upon nucleotide binding, it undergoes a conformational change that allosterically induces Pol II towards a post-translocation state. We propose this mechanism may help restart Pol II elongation and therefore contribute to reduction of transcription stress.

molecular biology↗

bioRxiv2024

Fe starvation induces a second LHCI tetramer to photosystem I in green algae

Iron (Fe) availability limits photosynthesis at a global scale where Fe-rich photosystem (PS) I abundance is drastically reduced in Fe-poor environments. We used single-particle cryo-electron microscopy to reveal a unique Fe starvation-dependent arrangement of light-harvesting chlorophyll (LHC) proteins where Fe starvation-induced TIDI1 is found in an additional tetramer of LHC proteins associated with PSI in Dunaliella tertiolecta and Dunaliella salina. These cosmopolitan green algae are resilient to poor Fe nutrition. TIDI1 is a distinct LHC protein that co- occurs in diverse algae with flavodoxin (an Fe-independent replacement for the Fe-containing ferredoxin). The antenna expansion in eukaryotic algae we describe here is reminiscent of the iron-starvation induced (isiA-encoding) antenna ring in cyanobacteria, which typically co-occurs with isiB, encoding flavodoxin. Our work showcases the convergent strategies that evolved after the Great Oxidation Event to maintain PSI capacity.

plant biology↗

bioRxiv2023

A proposed function for the red body of Nannochloropsis in the formation of the recalcitrant cell wall polymer, algaenan

Stramenopile algae contribute significantly to global primary productivity, and one class, Eustigmatophyceae, is increasingly studied for applications in high-value lipid production. Yet much about their basic biology remains unknown, including the nature of an enigmatic, pigmented globule found in vegetative cells. Here, we present an in-depth examination of this "red body", focusing on Nannochloropsis oceanica. During the cell cycle, the red body formed adjacent to the plastid, but unexpectedly it was secreted and released with the autosporangial wall following cell division. Shed red bodies contained antioxidant ketocarotenoids, and overexpression of a beta-carotene ketolase resulted in enlarged red bodies. Infrared spectroscopy indicated long-chain, aliphatic lipids in shed red bodies and cell walls, and LC-HRMS detected a C32 alkyl diol, a potential precursor of algaenan, a recalcitrant cell wall polymer. We propose that the red body transports algaenan precursors from plastid to apoplast to be incorporated into daughter cell walls.

cell biology↗